<!DOCTYPE html>
   <html>
       <meta name="content-type" content="text/html; charset=UTF-8">
      <head>
           <title>Calculator</title>
           
           <!--将按键内容以字符串形式存储在文字框中当按钮为“=”时，调用eval方法计算结果然后将结果输出文字框中-->
   
   <script type="text/javascript">
      var numresult;
      var str;
      
      function onclicknum(nums) {
  
          str = document.getElementById("nummessege");
          str.value = str.value + nums;
 
      }
  
      function onclickclear() {
  
          str = document.getElementById("nummessege");
          str.value = "";
  
      }
  
     function onclickresult() {
  
          str = document.getElementById("nummessege");
          numresult = eval(str.value);
          str.value = numresult;
          
      }
  </script>
  
      </head>
  
      <body bgcolor="affff" >
      
     <!--定义按键表格,每个按键对应一个事件触发-->
      
          <table border="1" align="center" bgColor="#bbff77"
              style="height: 350px; width: 270px">
             <tr>
                  <td colspan="4">
                      <input type="text" id="nummessege"
                          style="height: 90px; width: 350px; font-size: 50px" />
                  </td>
              </tr>
              <tr>
                  <td>
                      <input type="button" value="1" id="1" onclick="onclicknum(1)"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                  <td>
                      <input type="button" value="2" id="2" onclick="onclicknum(2)"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                  <td>
                      <input type="button" value="3" id="3" onclick="onclicknum(3)"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                  <td>
                      <input type="button" value="+" id="add" onclick="onclicknum('+')"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
              </tr>
  
              <tr>
                  <td>
                      <input type="button" value="4" id="4" onclick="onclicknum(4)"
                         style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                  <td>
                      <input type="button" value="5" id="5" onclick="onclicknum(5)"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                  <td>
                      <input type="button" value="6" id="6" onclick="onclicknum(6)"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                  <td>
                      <input type="button" value="-" id="sub" onclick="onclicknum('-')"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
              </tr>
  
              <tr>
                  <td>
                      <input type="button" value="7" id="7" onclick="onclicknum(7)"
                          style="height: 70px; width: 90px; font-size: 35px">
                  </td>
  
                 <td>
                     <input type="button" value="8" id="8" onclick="onclicknum(8)"
                         style="height: 70px; width: 90px; font-size: 35px">
                 </td>

                 <td>
                    <input type="button" value="9" id="9" onclick="onclicknum(9)"
                        style="height: 70px; width: 90px; font-size: 35px">
                 </td>
 
                 <td>
                     <input type="button" value="*" id="mul" onclick="onclicknum('*')"
                         style="height: 70px; width: 90px; font-size: 35px">
                 </td>
             </tr>
 
             <tr>
                 <td colspan="2">
                    <input type="button" value="0" id="0" onclick="onclicknum(0)"
                         style="height: 70px; width: 190px; font-size: 35px">
                 </td>
                 <td>
                     <input type="button" value="." id="point" onclick="onclicknum('.')"
                         style="height: 70px; width: 90px; font-size: 35px">
                 </td>
 
                 <td>
                     <input type="button" value="/" id="division"
                         onclick="onclicknum('/')"
                         style="height: 70px; width: 90px; font-size: 35px">
                 </td>
             </tr>
 
            <tr>
 
                 <td colspan="2">
                     <input type="button" value="Del" id="clear"
                         onclick="onclickclear()"
                         style="height: 70px; width: 190px; font-size: 35px" />
                 </td>
 
                 <td colspan="2">
                     <input type="button" value="=" id="result"
                        onclick="onclickresult()"
                         style="height: 70px; width: 190px; font-size: 35px" />
                 </td>

 
            </tr>
 
 
         </table>
    </body>
 </html>